Question Answered: What could be causing a slight thumping noise coming from the tires/wheels/area?
June 24, 2011, 04:11 PM
This sounds familiar. Following a quite detailed assessment by two different mechanics at my shop (which I trust), the conclusion was that the slight knocking sound I'd been hearing was actually most likely coming from the transmission and was most likely benign, especially if it doesn't get louder over time. The Getrag transission is supposed to be quite bulletproof. The most probably explanation (from the shop's senior technician, with 25 years experience, much of it with BMW) was that the sound was due to play between the gears themselves (being moved by the residual effect of the driveshaft still spinning), since the sound disappears under load. In other words, coming to a stop in neutral or with the clutch pedal depressed there is the slight knocking sound, but with the transmission engaged and under load (either accelerating or decelerating) the sound is not apparent.
Hope this is helpful. I've decided not to worry, as long as the sound does not change or get worse (and so far, after 3,000 miles with the car, it hasn't)...
Car Review: 2003 BMW Z4
June 24, 2011, 04:40 PM
Overall this is a great sports car, in my humble opinion.
The styling is not for some, but I happen to love it -- nice not to see yourself coming and going, as they say. Handling and steering response like a go kart, and the 2.5 liter is quite peppy (but yet gets good gas mileage and is said to be indestructible).
The overly harsh ride and squirlyness over pavement imperfections can be much improved by replacing the stock Bridgestone Potenzas with Michelin Pilot Sport PS2 runflat tires. (Actually it's the ride that's much improved; the squirlyness disappears altogether.) (Or you could switch from runflats and go with Goodyear Eagles and probably notice vast improvement as well, but there are trunk space and other benefits to runflat tires...)
Basically it's your classic late-60s British sports car updated by BMW, and thus with rock-solid reliability, impeccable handling, and great overall sporting driveability. (They don't call them Ultimate Driving Machines for nothing...)
In short, a perfect car for canyon roads, weekends, and mid-life crises of all sorts.